The Challenger launch decision
When the Space Shuttle Challenger exploded on January 28, 1986, millions of Americans became bound together in a single, historic moment. Many still vividly remember exactly where they were and what they were doing when they heard about the tragedy. In The Challenger Launch Decision, Diane Vaughan recreates the steps leading up to that fateful decision, contradicting conventional interpretations to prove that what occurred at NASA was not skulduggery or misconduct but a disastrous mistake.
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- And yet, deadly disasters do happen. https://en.wikipedia.org/wiki/Sayano-Shushenskaya_power_stat...
Key: "It seems they were used to the high levels of vibration" - Diane Vaughan wrote an important book that introduced the term "normalisation of deviance" as a factor in the Challenger Launch Decision, a more famous complex accident.
Another way of putting it is that "all complex systems operate in a degraded mode all the time", paraphrasing Adrian Colyer: https://blog.acolyer.org/2016/02/10/how-complex-systems-fail
- Not Seth's best post.
Sometimes when you get harsh feedback it has to do with (1) you, (2) people like you, (3) what somebody imagines you are.
I'd point to the idea of "weak signals" from
https://www.amazon.com/Challenger-Launch-Decision-Technology...
Roughly that organizations that are sensitive to weak signals have some protection from dangerous situations. I could ask, for instance, "Why is Amazon still here but K-Mart isn't?" and I'd answer: "There was that time I went shopping for new numbers from my mailbox and K-Mart had only a 4 and a 7 but not a 2".
I walked out buying none of the numbers and never gave anyone at K-Mart feedback about it because I didn't think anyone cared, that anyone was empowered to do anything about it. Had I brought it up I imagine they would have made some excuse along the lines "2 out of 3 ain't bad".
Given that K-Mart wasn't sensitive to weak signals I imagine the only person who would give feedback was somebody feeling hostile and sadistic who mainly wanted to raise the blood pressure of the manager. The one way you'd think you could make a difference by talking to them is by causing so much distress you could force somebody to quit and at least that person would get a job at an organization that could better use their talent.
Thus if you really have a culture which isn't sensitive to mild feedback the only feedback you're going to get is from people who "lose their shit."
- That's a really good summary / perspective. The more I read the Challenger Launch Decision, the more I was convinced that mistakes like the Challenger are unavoidable. We can try to reduce the risk, but given that we're always operating with limited resources, we just can't eliminate all the risks (from the design and implementation as well as the decision making and operation).
But "normalization of deviance" is also partially how the science / the engineering works. The science and engineering is pushing the boundary and turning what used to be unknown into known and tested through experiment / experience. Learning from experience is fundamentally how the science and the engineering work. So it's really difficult to tell when it's a normalization of deviance and when it's a normal scientific/engineering process.
- One of the reasons I really like Challenger Launch Decision is because it does a very good job of avoiding the hindsight bias as much as possible, by getting the readers to understand the perspective and the cultural norm of the organizations and participants, and tracing the decision making process itself and influences on those, instead of technical decisions themselves that were / might have been wrong in hindsight.
In hindsight, we can see mistakes in terms of specific design and technical decisions. But I don't think those are the biggest lessons from the disaster. We will continue making such mistakes, since technical misjudgement itself will always happen. I think Challenger Launch Decision's main point, that the organizational structure and culture have large impact on individual decision making is the lasting lesson. The book's closing sentence is excellent:
"The lingering uncertainty in the social control of risky technology is how to control the institutional forces that generate competition and scarcity and the powerful leaders who, in response, establish goals and allocate resources, using and abusing high-risk technical systems".
- The article draws on the definitive text in this area by Diane Vaughan[0]. Read her work on the Challenger Launch Decision - it goes into the details of why the deviance was normalised. Even down to the level of how important decision making conference calls marginalised technical inputs.
https://en.wikibooks.org/wiki/Professionalism/Diane_Vaughan_...
- >But the Challenger didn't explode because of Silly Shirt Friday. It exploded because management didn't respect their engineers.
That's a myth. I encourage you to read Challenger Launch Decision, by Diane Vaughan. Challenger didn't explode because management disrespected their engineers. Challenger exploded because the engineers themselves normalized deviance. They would launch, observe anomalous results, note that the system hadn't failed, and then expand the envelope of normality to include the anomalous results. At no point did the team working on the SRBs say, "No, we should stop the Shuttle program and redesign the booster," not even to other engineers. Repeatedly, in interviews, engineers expressed surprise and shock at the failure, because they thought that the problem of O-ring blow-by was a minor problem that could be fixed with tweaks. Indeed, on many an occasion, they thought that they had fixed it, only for the issue to recur in the future.
It's easy and comforting for us engineers to think that Challenger was due to myopia on the behalf of NASA management. But it's wrong. Challenger was the result of cascade failure of rationality all throughout the NASA organization, and the engineers are as culpable as the managers.
